Reciprocating hydraulic pumps



INVENTOR:

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Nov. 20, 1962 Filed July 6, 1960 Nov. 20, 1962 c. w. TRIDGELL 3,064,581

RECIPROCATING HYDRAULIC PUMPS Filed July 6, 1960 5 Sheets-Sheet 2 V ////iV --F I G. 3.-

' INVENTOR Cyril Vii ridge ATTome C. W. TRIDGELL RECIPROCATING HYDRAULIC PUMPS Nov. 20, 1962 5 Sheets-Sheet 5 Filed July 6, 1960 A+Torney Nov. 20, 1962 c. w. TRIDGELL RECIPROCATING HYDRAULIC PUMPS 5 Sheets-Sheet 4 Filed July 6, 1960 Nov. 20, 1962 c. w. TRIDGELL RECIPROCATING HYDRAULIC PUMPS 5 Sheets-Shet 5 Filed July 6, 1960 vs r w A m a r r b 33364531 RECIPROCA'I'ING HYDRAULIC PUMPS Cyril William Tridgell, Hemel Hempstead, England, assignor to Power Hacks Limited, a British company Filed July 6, 1969, Ser. No. 41,050 Claims priority, application Great Britain July 10, 1959 4 Claims. (Cl. 103-37) This invention relates to reciprocating hydraulic pumps and particularly, though not exclusively, to hydraulic pumps adapted to be manually actuated, i.e. by hand lever or pedal and such as are used to actuate hydraulic jacks, clamps or other hydraulically actuated devices.

In connection with hydraulically-actuated devices, it is often desired to have a dual-range pump, as distinct from a 2-stage pump in which a first low-pressure stage feeds a second high-pressure output stage; that is to say, by dual-range pump is meant one which is capable of delivering either a large volume at low pressure or a smaller volume at higher pressure, the former to bring the jack, clamp or other device quickly into its operative position or to operate against relatively light loads, and the latter to provide greater mechanical advantage as the load is taken up, or when dealing with heavier loads. Preferably, of course, such pumps are double-acting; that is to say, pumping occurs in both directions of movement of the actuating lever.

Double-acting dual-range pump units are already well known, but, hitherto, have consisted essentially of two individual pumps, both of which operate for low-pressure use, but one of which is open-circuited when the unit is required for high pressure use. Change-over from low to high pressure or vice versa is not usually automatic, and the unit assembly entails all the parts for two separate pumps mechanically coupled for simultaneous reciprocation.

One object of the present invention is a double-acting dual-range pump unit of improved construction embodying less parts than would be required for two separate pumps and having only three displacement chambers which are adapted to be hydraulically coupled in parallel or ditferential arrangement for lowor high-pressure operation respectively.

Another object of the invention is a double-acting dualrange hydraulic pump as aforesaid which is pressureresponsive for automatic change of range between lowpressure and high-pressure functioning.

A still further object of the invention is to enable the. pump to be not only used either as a low-pressure or high-pressure pump, but alternatively, as a mediumpressure pump with medium-volume delivery.

According to the present invention, a reciprocating dual range hydraulic pump comprises, in combination, one double-acting piston-and-cylinder assembly and one singleacting pump with non-return inlet and outlet valves for the three displacement chambers provided, in combination with control means for a connecting passage between the two chambers of the double-acting assembly such that the closing of said passage causes the pump direction to deliver alternately from one of said two chambers and from both the second of said two chambers and the single chamber of the other assembly, whilst the opening of said passage causes the pump to deliver alternately the differential volume of said two chambers and the volume of said single chamber less the negative differential volume of said two chambers.

In a preferred embodiment of the invention, the piston of the double-acting assembly has a piston rod at each end, one such rod being used for actuation of said piston and the other as the plunger of the single-acting assembly.

Patented Nov. 20, 1962 According to a further feature of the invention, the control means comprises a valve adapted automatically to open the associated passage when the pressure on the output side of the pump exceeds a predetermined value.

According to a still further feature of the invention, the non-return inlet valve to the chamber of the singleacting assembly is bridged by a manual valve whose opening causes the pump to operate as a medium-pressure unit delivering only from alternate chambers of the double-acting assembly.

In the accompanying drawings;

FIG. 1 is a central sectional side elevation of one example of a reciprocating dual-rangehydraulic pump for manual operation and made in accordance with the present invention.

FIG. 2 is a plan view of the pump of FIG. 1 with the cover removed.

FIG. 3 is an unfolded section on the line of FIG. 2.

FIGS. 4 and 5 are diagrammatic views showing the action of the pump during upand down-strokes respectively of the piston, when operating against low-pressure resistance.

FIGS. 6 and 7 are diagrammatic views showing the action of the pump during upand down-strokes respectively of the piston, when operating against high-pressure resistance.

FIGS. 8 and 9 are further diagrams showing two modifications of the pump and in accordance with the present invention.

In the constniction illustrated in FIGS. 1 to 3, an aluminium reservoir casting 10 has lugs 11 for the attachment of a cover 12, to the underside of which the body 13 of the pump unit is secured by bolts 14. Within such body a cylinder liner 15 is located between an upper gland assembly 16 and a lower gland assembly 17, the lower part of such liner being reduced in external diameter at 1511 and formed with through holes 151). Slidable within the liner 15 is a piston 18 provided at its upper side with an actuating piston rod 19 and at its lower side with a separate piston road 20 serving as a pump plunger. The piston is secured by means of a spring ring 18a against a shoulder formed at the junction of the rods 18, 2.0, a sealing ring 21 being also provided at such shoulder. The lower piston rod or plunger 20 has an axial bore 2tia and i fitted at its free end with a non-return inlet valve 22. Adjacent the shoulder aforesaid diametrally-opposed ports 20!) enable hydraulic fluid entering through the bore 20a to reach the lower end of the cylinder below the piston 18. The upper and lower chambers of the cylinder are designated A and B respectively, and within the pump body 13 is formed a third displacement chamber C in which works the plunger 2%) aforesaid, the cross-sectional areas of the several chambers being relatively important and suitable proportions thereof being given later herein.

Within the pump body 13 are formed several communicating passages including an inlet passage 23 whose lower end communicates with the displacement chamber 0 through a non-return inlet valve 24 and passage 24a and whose upper end is provided with a non-return valve 25 controlling a passage 26 which communicates with upper chambers A of the cylinder by way of an outer circumferential groove 15c and ports 15d in the wall of the liner 15. At its lower end the halet passage 23 is fitted with a filter 27.

The outlet passages in the pump body 13 comprise a bore 28 whose upper end communicates with the cylinder chamber A by way of a cross passage 29 leading to the liner groove 15c and Whose lower part communicates with the cylinder chamber B by way of a cross passage 30 leading to the externally relieved portion 15a of the liner. Within the lower part of the bore 28, which thus provides a connecting passage between the chambers A, B, is slidably mounted a close-fitting valve rod 3 1 urged by a spring 32 towards a position in which it prevents transfer of fluid between the chambers aforesaid, this spring being adjustably loaded by a screw plug 32a. Parallel with the bore 28 is the final outlet passage 33 which communicates with the cross passages 29, 30 by way of non-return valves 34, 35 respectively.

Also with-in the pump body 13 and in communication with the final outlet passage 33 (FIG. 3)' is a pressure release device consisting of a spring-loaded ball 36 and a plunger 37 adapted, when screwed down, to unseat such ball and thereby permit return of hydraulic fluid into the reservoir by way of the tube 38. A safety pressure-relief valve is fitted at 39 (FIG. 2) and a filler plug is provided at 40 in the cover 12. On top of the latter is a mounting bracket 41 for the L shaped actuating lever 42, whose shorter arm carries slide-blocks 43 engaged with the upper end of the piston rod 19.

During operation of the unit as a low-pressure pump, as shown in FIGS. 4 and 5, the valve rod 31 prevents communication between the chambers A, B, so long as the pressure in the connecting passage 28 is below a predetermined value determined by the strength of the spring 32 and the setting of its adjusting plug 32a. On the upward stroke of the piston 18 (FIG. 4), the delivery volume is represented by the capacity of the upper cylinder chamber A the valves 25, 35 being closed and the valves 22', 24, 34 being open. On the downward stroke of the piston (FIG. 5), the delivery volume con-', sists of the combined capacities of the chambers B, C, the valves 24, 34 being closed and the valves 22, 25, 35 being open,

When the pressure in the connecting passage 28 be comes sufficient to push back the valve rod 31 therein, as shown in FIGS. 6 and 7, communication is established between the chambers A, B. On the upward stroke of the piston 18, the delivery is a differential volume comprising the capacity of the chamber A minus that of the chamber B, this reduction of the delivery volume enabling the operator to work against higher pressures without having to exert greater force on the lever 42. During this stroke, the valves 22, 25 are closed whilst the valve 24 and either. or both of the valves 34, 35 open to pass the delivery volume to the final outlet passage 33. On the downward stroke, the delivery volume will be equal to the displacement of the piston rod 19, which is nearly the same as the combined capacity of the chambers B, C less that of the chamber A.

In the modification shown in FIG. 8, a further nonreturn valve 44 is provided in the main inlet passage 23,

as well as a manually-operable valve 45 by-passing the non-return valve 24. Ifthe valve 45 is opened, then the single-acting pump represented by the plunger 20 in the chamber C becomes inoperative whilst the piston 18 and cylinder function as a normal double-acting whether to work the pump on, maximum or reduced delivery rate.

Convenient proportions for the cross-sectional areas of the upper and lower cylinder chambers A and B, the plunger and the piston rod 19 are as follows:

Chamber A=.921 Chamber B=.626 Plunger 20 Chamber 0 i Piston-rod 19:.306

4 On this basis the delivery volume per unit distance of piston travel will be in the following ratios- Low pressure:

Up=.921=A DOWn=1 227:B C Mean volume=1.074

(The maximum force required is, therefore, determined by the down stroke.)

High pressure:

Up: .295 =A--B Down=.3 06=BCA (displacement of piston-rod 16) Mean volume =.300

Intermediate pressure (FIG. 8):

gzaii gigl Mean volume=.774

(The maximum force required is deterrniued by the up stroke.)

The invention is obviously not limited to all the details above set forth and illustrated, these being given by way of example only and some of them being capable of modification without departure from the scope of the invention.

I claim:

1. A reciprocating dual-pressure hydraulic pump with pressure-sensitive valve means for automatic change-over the piston and plunger simultaneously, automatic inletvalves for one end of each cylinder, a passage connecting the other end of the large cylinder with the smaller cylinder, a non-return valve allowing'fluid to pass through said passage from the smaller cylinder, outlet passages from each end of the largercylinder, non-return valves in each outlet passage, a transfer passage connecting the said outlet passages, said transfer passage being disposed between said cylinders and said non-return valves, a piston valve.

operable in said transfer passage, said piston valve adapted to enter said transfer passage from the one of said outlet passages which is connected to the said other end of the large cylinder, and spring means urging the said piston valve into said passage to close the same.

' 2. A reciprocating pump as claimed in claim 1 char-.

acterized by a manually controllable valve and by-pass for the inlet valve of the smaller cylinder.

3.jA reciprocating pump as claimed in claim 1 chari acterized in thatthe passage connecting" the end of the large cylinder with the smaller cylinder is formed in the plunger.

I 4. A reciprocating pump as claimed in claim 3 char-.

acterized in thatthe non-return outlet valves are connected to the ends of said transfer passage which is controlled by said piston valve.

References Cited in the file of this patent UNITED STATES PATENTS 2,410,808 Christensen Nov. 12, 1946 2,686,477 Hoschle et a1. Aug. 17, 1954 2,989,001 Wilkenloh et al June 20, 1961 q FOREIGN PATENTS 565,125 France Ian. 19, 1924 1,075,780 France Apr. 14, 1954 OTHER REFERENCES German application (KLSC-lO/Ol), 1,007,715, May 9, 1957. 

